2 -1 0 -1 0 0 0 0 0
-1 3 -1 0 -1 0 0 0 0
0 -1 2 0 0 -1 0 0 0
-1 0 0 3 -1 0 -1 0 0
0 -1 0 -1 4 -1 0 -1 0
0 0 -1 0 -1 3 0 0 -1
0 0 0 -1 0 0 2 -1 0
0 0 0 0 -1 0 -1 3 -1
0 0 0 0 0 -1 0 -1 2
________________________________
From: SPM (Statistical Parametric Mapping) <[log in to unmask]> on behalf of Ming Teng <[log in to unmask]>
Sent: 14 December 2016 16:26
To: [log in to unmask]
Subject: Re: [SPM] A question regarding Laplacian matrix in SPM12
And by saying edge, I mean the neighbors. Thanks.
On Wed, Dec 14, 2016 at 11:23 AM, Ming Teng <[log in to unmask]<mailto:[log in to unmask]>> wrote:
Dear SPM experts,
I have a question regarding the Unweighted Graph Laplacian matrix in SPM12. By assuming a 2d slice, my question is, when the voxel is located on the boundary of the mask, which has fewer than 4 neighbors, what is the form of the UGL like?
According to "Penny et al 2005", the UGL matrix will still have 4 on the diagonal component, and -1 on the edges that are inside the mask, and 0 on the edges that are outside the mask. Can anyone help me confirm this? Thanks a lot!
Sincerely,
Ming
